Machine tool

ABSTRACT

The present invention provides a machine tool whose width dimension is not increased even when it includes a tool magazine. The present invention includes: a bed  2;  a saddle  4  disposed on the bed  2  to be movable in a forward and backward (Y-axis) direction in a front view of the machine tool; a table  5  disposed on the saddle  4  to be movable in right and left (X-axis) direction; a column  3  fixed on the bed  2;  a spindle head  6  disposed on the column  3  to support a spindle  7  and movable in a vertical (Z-axis) direction; an automatic tool changer  10  disposed on a back face side of the column  3,  wherein the column  3  has an opening A which allows the back face  3   b ″ side and a front face  3   b ′ side of the column  3  to communicate with each other, and the automatic tool changer  10  replaces a tool T on the spindle  7  side by a tool T 1  on a tool magazine  11  side through the opening A.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 10/891,491 filed on Jul. 15, 2004, currently pending. Thedisclosure of U.S. patent application Ser. No. 10/891,491 is herebyincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a machine tool that machines aworkpiece while moving a vertically set spindle and the workpiecerelatively to each other in X-axis, Y-axis, and Z-axis directions.

2. Description of the Related Art

For example, a vertical machining center that machines a workpiece usinga table movable in X-axis and Y-axis directions and a spindle movable ina Z-axis direction is generally structured, as shown in FIG. 10, toinclude: a column 61 fixedly disposed on a back end of a fixed bed 60when seen from a front side of the machine; a saddle 62, for placing aworkpiece W thereon, disposed on a front part of the fixed bed 60 to bemovable in the Y-axis direction (forward and backward direction); atable 63 disposed on the saddle 62 to be movable in the X-axis direction(right and left direction); and a spindle head 65, with a spindle 64attached thereto, disposed on a front face of the column 61 to bemovable in the Z-axis direction (vertical direction).

In some conventional vertical machining centers of this type, a toolmagazine 66 of an automatic tool changer is disposed on a side face ofthe column 61 for replacing a preceding working tool T attached to thespindle 64 by a subsequent working tool housed in the tool magazine 66.

SUMMARY OF THE INVENTION

A problem of the above-described conventional machine, in which the toolmagazine is disposed on the side face of the column, is that the widthdimension of the machine is naturally increased.

It is an object of the present invention to provide a machine tool whosewidth dimension is not increased even when it includes a tool magazine.

In an invention, a machine tool includes: a bed; a saddle disposed onthe bed to be movable in a forward and backward (Y-axis) direction in afront view of the machine tool; a table disposed on the saddle to bemovable in right and left (X-axis) direction; a column fixed on the bed;a spindle head disposed on the column to support a spindle and movablein a vertical (Z-axis) direction; an automatic tool changer disposed ona back face side of the column, wherein the column has an opening whichallows the back face side and a front face side of the column tocommunicate with each other, and the automatic tool changer replaces atool on the spindle side by a tool on a tool magazine side through theopening.

In the invention, the automatic tool changer is disposed on the backface side of the column and it replaces the tool on the spindle side bythe tool on the tool magazine side through the opening allowing the backface side and the front face side of the column to communicate with eachother, so that it is possible to utilize a vacant space on the back faceof the column for disposing the tool magazine. This can prevent theincrease in the width dimension of the machine.

In a preferable embodiment of the invention, the column has a shape of agate that is bridged over a travel range of the table and has right andleft legs and a beam connecting tops of the right and left legs, and theautomatic tool changer is disposed on a back face side of the beam ofthe column and passes under a lower edge of the beam to replace the toolon the spindle side by the tool on the tool magazine side.

In the above-described embodiment, the column has the shape of the gatebridged over the travel range of the table with the beam connecting thetops of the right and left legs, so that it is possible to effectivelyutilize, for tool replacement, a machining opening under the columntool. This eliminates the need for separately saving a space for toolreplacement, so that the overall machine tool can be made compact.

In another preferable embodiment of the invention, the beam of thecolumn is displaced from the right and left legs toward a back face sideof the machine tool and is set above the bed at a substantially centerportion of the bed in terms of the Y-axis direction.

In the above-described embodiment, since the beam of the column isdisplaced from the right and left legs toward the back face side of themachine tool and is set at the substantially center portion of the bedin terms of the Y-axis direction, it is possible to effectively utilizea vacant space of the back face side of the beam for disposing the toolmagazine, so that the overall machine tool can be made compact.

In still another preferable embodiment of the invention, the automatictool changer includes: a tool magazine disposed on the back face of thebeam of the column; a change arm shaft vertically passing through thebeam; a change arm turnably connected to a lower end of the change armshaft; a change arm turn driving unit connected to an upper end of thechange arm shaft; and a tool transfer mechanism disposed in parallel tothe change arm shaft to transfer a tool between the tool magazine andthe change arm.

In the above-described embodiment, the change arm shaft is disposed tovertically pass through the beam and the tool transfer mechanism isdisposed in parallel to the change arm shaft, so that it is possible todispose a tool change unit on the back face side of the beam withreduced installation space necessary.

BRIEF DESCRIPTION OF THE DRAWINGS

The structure, operation, and effect of the present invention will bedetailed in an embodiment based on the following attached drawings.

FIG. 1 is a front view to explain a vertical machining center accordingto an embodiment of the present invention;

FIG. 2 is a right side view of the vertical machining center;

FIG. 3 s a plane view of the vertical machining center;

FIG. 4 is a rear perspective view of the vertical machining center;

FIG. 5 is a rear view of the vertical machining center;

FIG. 6 is a left side view of the vertical machining center;

FIG. 7 is a side view showing the structure of a tool changer providedin the vertical machining center;

FIG. 8 is a schematic perspective view of a workpiece changer of thevertical machining center;

FIG. 9 is a schematic side view of the workpiece changer; and

FIG. 10 is a schematic view of a typical vertical machining center of aconventional art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment of the present invention will be hereinafter describedbased on the attached drawings.

FIG. 1 to FIG. 9 show a vertical machining center 1. The machiningcenter 1 includes a gate-shaped column 3 fixed on a substantially centerportion of a fixed bed 2 in terms of a forward and backward direction, asaddle 4 disposed under the column 3 to be movable in a Y-axis (forwardand backward) direction, a table 5 disposed on the saddle 4 to bemovable in an X-axis (right and left) direction, and a spindle head 6disposed on a front face of the column 3 to be movable in a Z-axis(vertical) direction. A spindle 7 is rotatably supported by a lower endof the spindle head 6, and a tool T is detachably attached to thespindle 7.

In the vertical machining center 1 described above, a workpiece (notshown) placed on the table 5 is machined by the tool T while theworkpiece and the spindle 7 are moved relatively to each other, theworkpiece moving in the X-axis and Y-axis directions and the spindle 7moving in the Z-axis direction.

On a back face side of the fixed bed 2, mounted is a workpiece changer12 that turns 180 degrees a preceding process pallet P1 on which amachined workpiece is placed and a subsequent process pallet P2 on whicha subsequently machined workpiece is placed, via a turn shaft 37,thereby automatically replacing these pallets P1, P2. Further, a chipdisposer 13 is provided on a bottom of the fixed bed 2. The chipdisposer 13 includes a conveyor 47 and a coolant tank 48, the conveyor47 collecting a cutting fluid supplied to a workpiece machining portionand discharging chips produced by workpiece machining out of themachine.

The fixed bed 2 includes right and left vertical walls 2 a, 2 a, saddlesupports 2 b, 2 b formed in a stepped shape inside the right and leftvertical walls 2 a, and a substantially flat bottomed recession 2 cstepped down from the right and left saddle supports 2 b. This bottomedrecession 2 c is positioned at a center portion of the bed 2 in terms ofthe X-axis direction with a back face side and an upper face sidethereof opened. The right and left vertical walls 2 a on the back faceside of the fixed bed 2 are coupled to each other with a cross member 8.

Right and left Y-axis guide rails 15 supportingly guiding the saddle 4in the Y-axis direction extend along inner edges of the right and leftsaddle supports 2 b. Each of the Y-axis guide rails 15 includes a rail15 a fixed to the saddle support 2 b and a guide 15 b fixed to a bottomface of the saddle 4, the rail 15 a and the guide 15 b being slidablyfitted to each other.

Further, right and left Y-axis ball screws 16, 16 for driving themovement of the saddle 4 in the Y-axis direction are rotatably fixed toouter sides of the respective Y-axis guide rails 15 on the right andleft saddle supports 2 b, and Y-axis drive motors 17, 17 for driving therotation of the ball screws 16 are connected to front ends of therespective Y-axis ball screws 16.

A pair of front and back X-axis guide rails 18, 18 for supportinglyguiding the table 5 in the X-axis direction are disposed on a top faceof the saddle 4. Each of the X-axis guide rails 18 includes a rail 18 afixed to the saddle 4 and a guide 18 b fixed to a bottom face of thetable 5, the rail 18 a and the guide 18 b being slidably fitted to eachother.

Between the front and back X-axis guide rails 18 on the top face of thesaddle 4, one X-axis ball screw 19 for driving the movement of the table5 in the X-axis direction is rotatably fixed, and an X-axis drive motor20 for driving the rotation of the ball screw 19 is connected to a leftend of the X-axis ball screw 19.

A pair of right and left Z-axis guide rails 21, 21 for supportinglyguiding the spindle head 6 in the Z-axis direction is disposed on thefront face of the column 3. Each of the Z-axis guide rails 21 includes arail 21 a fixed to a back face of the spindle head 6 and a guide 21 bfixed to the front face of the column 3, the rail 21 a and the guide 21b being slidably fitted to each other.

Right and left Z-axis ball screws 22, 22 for driving the movement of thespindle head 6 in the Z-axis direction are rotatably fixed on outersides of the respective Z-axis guide rails 21 on the front face of thecolumn 3, and Z-axis drive motors 23, 23 for driving the rotation of theball screws 22 are connected to upper ends of the respective Z-axis ballscrews 22.

The spindle head 6 has arms 6 a, 6 a extending in the right and leftdirections, and nuts 22 a fitted to the Z-axis ball screws 22 areattached to the right and left arms 6 a.

The column 3 is formed integrally by casting and has a shape of a gatethat is bridged over an X-axis and Y-axis travel range of the table 5 ina front view of the machine and has right and left legs 3 a, 3 a and abeam 3 b integrally connecting tops of the right and legs 3 a. The rightand left legs 3 a are fixed on top faces of the right and left verticalwalls 2 a of the fixed bed 2. In this structure, a machining opening Awhich is opened in the Y-axis direction and whose width in the X-axisdirection is wide is formed under the column 3.

In a front view of the machine, the right and left legs 3 a are inclinedso that upper portions 3 d of the legs 3 a are positioned closer to thespindle head 6 and form a substantially triangular shape with thespindle head 6 side having larger vertical dimension. Further, the beam3 b are formed in a square shape with an upper edge and an open loweredge thereof being substantially parallel to each other.

In a plane view of the machine, the column 3 is formed in asubstantially arch shape so that the beam 3 b is displaced from theright and left legs 3 a, 3 a toward the back face side of the machine,and a front face 3 b′ of the beam 3 b substantially coincides with a legcenter line C1 passing through the centers of the right and left legs 3a in terms of the forward and backward direction. Further, the beam 3 bis positioned at a center of the fixed bed 2 in terms of the Y-axisdirection, and the right and left legs 3 a are positioned on a frontside thereof. A housing recession 3 c for housing the spindle head 6 andthe right and left Z-axis ball screws 22 is formed on the front face 3b′ of the beam 3 b. This structure eliminates the overhang of thespindle head 6 from the column 3.

Side wall recessions 2 d recessed outward in the right and leftdirections of the machine are formed in the right and left verticalwalls 2 a of the bed 2 respectively. Ends 18 c of the X-axis guide rails18 are positioned in the right and left side wall recessions 2 drespectively.

A tool changer 10 for automatically replacing a preceding working tool Tattached to the spindle 7 by a subsequent working tool T1 attached tothe tool magazine 11 through the opening A of the column 3 is mounted onthe column 3.

The tool changer 10 includes: the tool magazine 11 in a circular shapethat vertically holds a large number of tools Tn by a pot with the toolsTn facing downward and drives the turn of the subsequent working tool T1for indexing at a tool indexing position “a”; a tool transfer mechanism25 that transfers the subsequent working tool T1 indexed at the indexingposition “a” to a tool change position “b” and returns the precedingworking tool T, which is returned to the tool change position “b”, tothe tool magazine 11; and a change arm 26 replacing the precedingworking tool T, which is transferred to a tool change position “c” bythe spindle 7, by the subsequent working tool T1 transferred to the toolchange position “b”.

The tool magazine 11 is disposed on a back face 3 b″ of the beam 3 b ofthe column 3 and is suspendedly supported by a bracket 27 fixed to theback face 3 b″. Note that 11 a denotes a turn indexing motor.

A change arm shaft 28 is insertedly disposed on a back side of thespindle head 6 on the beam 3 b so as to vertically pass through the beam3 b. The change arm 26 is connected to a bottom end of the change armshaft 28, and a turn driving unit 29 for driving the change arm 26 toturn 180 degrees is connected to an upper end of the change arm shaft28. A drive motor 30 is connected to the turn driving unit 29. A balancespring 34 constantly biases the change arm shaft 28 upward to cancel theweight of the tool.

The tool transfer mechanism 25 includes: a direct acting guide 31disposed in a rectangular hole 3 e (see FIG. 3) formed on a back side ofthe change arm shaft 28 in the beam 3 b to be parallel to the change armshaft 28; a hook 32 supported by the direct acting guide 31 to bevertically movable and gripping the pot of the subsequent working toolT1; and an air cylinder 33 for driving the hook 32 to move up/downbetween the tool indexing position “a” and the tool change position “b”.

The change arm 26 is kept on standby under the lower edge of the beam 3b with its longitudinal direction aligned with the X-axis direction.Then, the change arm 26 replaces the preceding working tool T on thefront face 3 b′ side of the beam 3 b by the subsequent working tool T1on the back face 3 b″ side thereof through the opening A of the column3.

When the workpiece machining is finished, the spindle head 6 moves inthe Z-axis direction to locate the preceding working tool T at the toolchange position “c”, and the tool magazine 11 turns and indexes thesubsequent working tool T1 to locate it at the tool indexing position aThe hook 32 grips the pot of the subsequent working tool T1 indexed atthe tool indexing position “a”, and the air cylinder 33 transfers thesubsequent working tool T1 together with the hook 32 to the tool changeposition “b” to locate it at this change position “b”. The change arm 26turns from the standby position to grip the preceding working tool T aswell as the subsequent working tool T1, moves down in this state to takeout the tools T, T1, turns 180 degrees, and thereafter moves up. Throughthis operation, the preceding working tool T is placed in a pot kept onstandby at the tool change position “b”, and the subsequent working toolT1 is attached to the spindle 7. The preceding working tool T is liftedtogether with the hook 32 to be returned to the tool magazine 11.

The workpiece changer 12 is roughly structured such that a clamp 38 isfixed to an upper end of the turn shaft 37 disposed to beascendible/descendible and turnable 180 degrees. The clamp 38 hasgrooves 38 a, 38 a fittable to hooks 39, 40 formed in the aforesaidpallets P1, P2, and hydraulic pistons 41, 41 are disposed in therespective grooves 38 a to be projectable/retreatable. When thehydraulic pistons 41 protrude into the grooves 38 a, the pallets P1, P2are clamped and when they retreat out of the grooves 38 a, the palletsP1, P2 are unclamped.

The subsequent process pallet P2 is positioned at a workpiece standbyposition B that is set outside the machine on a back face side of thefixed bed 2, and the preceding process pallet P1 is positioned at aworkpiece change position C that is set under the column 3. Further, theturn shaft 37 is disposed on a back end of the fixed bed 2.

A subsequent machined workpiece is placed in the subsequent processpallet P2 at the workpiece standby position B in advance. When workpiecemachining is finished, the table 5 moves in the X-axis and Y-axisdirections to transfer the preceding process pallet P1 to the workpiecechange position C. The turn shaft 37 moves up, the hooks 39, 40 of thepallets P1, P2 are fitted in the respective grooves 38 a, and thehydraulic pistons 41 protrude to clamp the pallets P1, P2. The turnshaft 37 further moves up to lift the pallets P1, P2 from the table 5,turns 180 degrees in this state, and thereafter moves down. Through thisoperation, the preceding process pallet P1 and the subsequent processpallet P2 are placed at the workpiece standby position B and on thetable 5 at the workpiece change position C respectively.

According to this embodiment, the column 3 is in the gate shape in whichthe beam 3 b connects the tops of the right and left legs 3 a, 3 a, andis fixed on the top faces of the right and left vertical walls 2 a, 2 aof the fixed bed 2, being bridged over the travel range of the table 5,which allows the table 5 to move in the X-axis and Y-axis directionsthrough the opening A under the column 3. This enables the arrangementof the spindle shaft 6 on the column 3 without any overhang. As aresult, the allowable acceleration/deceleration value of the spindlehead 6 at the Z-axis direction feed time can be increased. In accordancetherewith, the feed rate can be increased to shorten the machining time,resulting in improved productivity.

Moreover, since the overhang of the spindle head 6 can be eliminated, itis possible to eliminate the influence to machining accuracy andeliminate the need for increased stiffness of the column 3 more thannecessary, resulting in reduced cost and weight.

Since the beam 3 b of the column 3 is positioned at the center portionof the fixed bed 2 in terms of the Y-axis direction, it is possible toset the Y-axis direction dimension of the fixed bed 2 substantiallyequal to the Y-axis stroke amount of the table 5. This structure canmake the overall machine compact compared with the conventionalstructure in which the column is disposed on the back end of the bed.

Further, the beam 3 b of the column 3 is displaced toward the back faceside of the machine so that the front face 3 b′ of the beam 3 bsubstantially coincides with the leg center line C1 of the right andleft legs 3 a, 3 a, and the axis of the spindle head 6 substantiallycoincides with the center line C1 of the legs 3 a. This structure caneliminate the overhang of the spindle head 6 from the right and leftlegs 3 a. Accordingly, it is possible to further increase the allowableacceleration/deceleration value of the spindle head 6, so that the feedrate can be further increased.

Moreover, since the right and left legs 3 a are inclined so that theupper portions 3 b are positioned closer to the spindle head 6, thelength in the X-axis direction of the beam 3 b can be shortened.Accordingly, the overall column can have increased stiffness and can bemade compact.

Further, the ends 18 c of the respective rails 18 a of the X-axis guiderails 18 are positioned in the recessions 2 d of the vertical walls 2 aof the fixed bed 2, so that it is possible to suppress the increase inwidth dimension of the machine body while securing the travel amount inthe X-axis direction of the table 5.

According to this embodiment, the automatic tool changer 10 is disposedon the back face 3 b″ side of the column 3 formed in the gate shape, andit replaces the preceding working tool T on the spindle 7 side by thesubsequent working tool T1 on the tool magazine 11 side through theopening A that allows the back face 3 b″ side and the front face 3 b′side of the column 3 to communicate with each other, so that the vacantspace of the back face 3 b″ of the column 3 can be utilized for placingthe tool magazine 11, which can prevent the increase in the widthdimension of the machine.

Since the column 3 is in the gate shape bridged over the travel range ofthe table with the beam 3 b connecting the tops of the right and leftlegs 3 a, the machining opening A formed under the column 3 can beeffectively utilized for tool replacement. This can eliminate the needfor a tool change space and can make the overall machine compact.

Further, the beam 3 b of the column 3 is displaced from the right andleft legs 3 a toward the back face side of the machine and is disposedat the center portion of the fixed bed 2 in terms of the Y-axisdirection, so that the vacant space on the back face 3 b″ side of thebeam 3 b can be effectively used for placing the tool magazine 11 andthe overall machine can be made compact.

Moreover, the change arm shaft 28 vertically passes through the beam 3b, and the tool transfer mechanism 25 is parallel to the change armshaft 28, so that it is possible to dispose a tool change unit such asthe change arm shaft 28 and the tool transfer mechanism 25 with reducedrequired arrangement space.

According to this embodiment, the column 3 is in the gate shape bridgedover the travel range of the table 5, the workpiece standby position Bis set outside the machine on the back face side of the fixed bed 2, andthe workpiece change position C is set under the column 3. Accordingly,it is possible to utilize the machining opening A under the column 3 forarranging the turn-type workpiece changer 12 on the back face side ofthe fixed bed 2. This structure realizes easy approachability to thespindle 7 from the front side of the bed 2 and improved work efficiencyof maintenance.

Further, the column 3 is in the gate shape with the beam 3 b connectingthe tops of the right and left legs 3 a, so that it is possible toeffectively utilize the machining opening A under the column 3 fordisposing the workpiece changer 12, which can make the overall machinecompact.

In addition, since the beam 3 b is displaced from the right and leftlegs 3 a toward the back face side of the machine and is positioned atthe center portion of the fixed bed 2 in terms of the Y-axis direction,it is possible to secure a turn space for workpiece replacement in thecenter portion of the bed and to further improve approachability to thespindle 7 from the front side of the bed.

Further, the workpiece standby position B is set outside the machine onthe back face side of the fixed bed 2 and the turn shaft 37 is disposedon the back end of the fixed bed 2, the workpiece attaching/detachingoperation can be facilitated and the increase in installation area ofthe workpiece changer 12 can be suppressed.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof.

The present embodiments are therefore to be considered in all respectsas illustrative and no restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

1. A machine tool comprising: a bed; a saddle disposed on said bed to bemovable in a forward and backward (Y-axis) direction in a front view ofthe machine tool; a table disposed on said saddle to be movable in rightand left (X-axis) direction; a column fixed on said bed; a spindle headdisposed on said column to support a spindle and movable in a vertical(Z-axis) direction; an automatic tool changer disposed on a back faceside of said column, wherein said column has an opening which allows theback face side and a front face side of said column to communicate witheach other, and wherein said automatic tool changer replaces a tool onsaid spindle side by a tool on a tool magazine side through the opening.2. The machine tool according to claim 1, wherein said column has ashape of a gate that is bridged over a travel range of said table andhas right and left legs and a beam connecting tops of the right and leftlegs, and wherein said automatic tool changer is disposed on a back faceside of the beam of said column and passes under a lower edge of thebeam to replace the tool on said spindle side by the tool on the toolmagazine side.
 3. The machine tool according to claim 2, wherein thebeam of said column is displaced from the right and left legs toward aback face side of the machine tool and is set above said bed at asubstantially center portion of said bed in terms of the Y-axisdirection.
 4. The machine tool according to claim 2, wherein saidautomatic tool changer includes: a tool magazine disposed on the backface of the beam of said column; a change arm shaft vertically passingthrough the beam; a change arm turnably connected to a lower end of thechange arm shaft; a change arm turn driving unit connected to an upperend of the change arm shaft; and a tool transfer mechanism disposed inparallel to the change arm shaft to transfer a tool between the toolmagazine and the change arm.
 5. The machine tool according to claim 3,wherein said automatic tool changer includes: a tool magazine disposedon the back face of the beam of said column; a change arm shaftvertically passing through the beam; a change arm turnably connected toa lower end of the change arm shaft; a change arm turn driving unitconnected to an upper end of the change arm shaft; and a tool transfermechanism disposed in parallel to the change arm shaft to transfer atool between the tool magazine and the change arm.